No data connection

I am a first time user of SmartFTP. This is part of what I get when I connect to my server. Please help.

[15:07:32] 200 PORT command successful.
[15:07:32] LIST -aL
[15:07:33] 150 Opening ASCII mode data connection for /bin/ls.
[15:07:38] 425 Can't open data connection.
[15:08:08] NOOP
[15:08:09] 200 NOOP command successful